Lazy Loading in Angular: A Beginner's Guide to Routing
Angular lazy loading routing web applications performance optimization network resources code splitting memory consumption

José Matos

25 Mar 2023

Lazy Loading in Angular: A Beginner's Guide to Routing

    Lazy Loading in Angular: A Beginner's Guide to Routing

    Angular is a popular framework for building dynamic and responsive web applications. One of its key features is its routing capabilities that allow developers to create complex and intuitive navigation structures. With the release of Angular 4, lazy loading was introduced which has revolutionized the way we build large-scale applications. In this article, we will discuss lazy loading and how it works with routing in Angular.

    What is Lazy Loading?

    Lazy loading is a technique that allows resources, such as modules or components, to be loaded on demand rather than upfront when the application is loaded. This technique significantly improves the performance of web applications by reducing initial load times and optimizing the use of network resources.

    In a traditional Angular application, all the necessary resources are loaded upfront, which can result in slower load times and increased network traffic. This can be particularly problematic in large-scale applications where many components and modules may be required.

    Lazy loading solves this problem by only loading resources when they are needed. For example, if a user navigates to a particular route in an application, only the resources required for that route are loaded at that time. This means that the application can be loaded more quickly and efficiently, enhancing the user experience.

    How does Lazy Loading work with Routing in Angular?

    Routing is a powerful feature of Angular that allows developers to create highly interactive and responsive applications. Lazy loading works seamlessly with routing in Angular, allowing resources to be loaded only when they are needed. Let's take a look at how this works in practice.

    First, we need to define our routes in our application. This is typically done in the app-routing.module.ts file as follows:

    import { NgModule } from '@angular/core';
    import { Routes, RouterModule } from '@angular/router';
    const routes: Routes = [
      { path: '', pathMatch: 'full', redirectTo: 'home' },
      { path: 'home', loadChildren: () => import('./home/home.module').then(m => m.HomeModule) },
      { path: 'about', loadChildren: () => import('./about/about.module').then(m => m.AboutModule) }
      imports: [RouterModule.forRoot(routes)],
      exports: [RouterModule]
    export class AppRoutingModule { }

    In this example, we have defined two routes: home and about. The loadChildren property specifies the module that is to be loaded when the route is activated. In this case, the HomeModule and AboutModule modules are loaded.

    It is important to note that lazy loading requires that each module has its own routing module. This is because each module needs to define its own routes.

    Next, we need to create the module that is to be loaded for each route. This can be done in the following way:

    import { NgModule } from '@angular/core';
    import { RouterModule, Routes } from '@angular/router';
    import { HomeComponent } from './home.component';
    const routes: Routes = [
      { path: '', component: HomeComponent }
      imports: [RouterModule.forChild(routes)],
      exports: [RouterModule]
    export class HomeRoutingModule { }

    Here, we have defined a single route with HomeComponent being loaded when the route is activated. The module is then imported into the main AppRoutingModule, as seen in the previous example.

    Lazy loading works by dynamically loading the module when the route is activated. This means that the module is only loaded when it is needed and not upfront when the application is loaded. This can result in significant performance improvements for larger applications.

    Benefits of Lazy Loading in Angular

    Lazy loading provides a number of benefits for Angular applications. Let's take a look at some of these benefits:

    • Improved performance: Lazy loading significantly improves the performance of web applications, reducing load times and optimizing network resources.
    • Better user experience: By reducing initial load times, users are able to navigate through the application more quickly and easily.
    • Code splitting: Lazy loading allows for code splitting which means that only the required code for a specific route is loaded. This can result in smaller bundle sizes, making the application more efficient.
    • Lower memory consumption: By only loading resources when they are required, memory consumption is reduced which can result in improved overall application performance.


    Lazy loading is a powerful technique that can greatly enhance the performance of Angular applications. When coupled with routing, it allows for the dynamic loading of resources, resulting in improved load times and optimized network performance. Understanding how lazy loading works is essential for building large-scale applications that are both efficient and responsive. By following the guidelines outlined in this article, you can take full advantage of this powerful feature and build better, faster Angular applications.

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